Electron discharge devices



March 27, 1962 E. c. DENCH 3,027,483

ELECTRON DISCHARGE DEVICES Filed May 27, 1953 2 Sheets-Sheet 1 //v VENTOR EDWARD C, DENC'H A TTORNE V March 27, 1962 E. c. DENCH 3,027,483

ELECTRON DISCHARGE DEVICES Filed May 27, 1953 30 2 Sheets-Sheet 2 ''axaaaaaaacxxx /llf/i INVEN'IC EDWARD C. DENC'H ATTO PNEV United States 3,@Z7,483 Patented Mar. 27, 1962 3,l327,433 ELECTRGN DESQHARGE DEVICES Edward C. Dench, Needharn, Mass, assignor to Raytheon Compan a corporation of Delaware Filed May 27, 1953, Ser. No. 357,824 11 Claims. (Cl. 3153.5)

This invention relates to an electron discharge device and. more particularly to a sole electrode and cathode mounting assembly for a backward wave traveling wave tube oscillator.

It is known that an oscillator tube may be made in which the radio frequency energy produced therein travels backwards against the electron stream to reach a load. Such an oscillator, like certain forms of the traveling wave tube, employs a slow wave guide and a magnetic field transverse to an electron beam passing along the wave guide. Thus, if radio frequency energy is allowed to travel along such a wave guide, the electromagnetic fields associated therewith will be comprised of an infinite series of traveling space harmonic waves, and some of these waves will flow in a direction opposite to that of energy flow. If an electron beam is sent in the direction of one of these opposite traveling waves, interaction will occur between the beam and the wave and the beam will give energy to the wave. The energy given to this wave will travel toward the source of the beam, thereby modulating the beam. When the beam current is sufiiciently great, the action becomes self-sustaining and oscillation will occur. Thus, the energy given to the wave by the beam will travel toward the source of the beam and may be extracted at that end of the wave guide and fed to a load.

Tubes of the type described above may be made in a circular cylindrical design, and the leads, bushings and exhaust tubulation therein may be disposed along a section of the circumference of the tube. The segment of the tube occupied by these members cannot be used as an area of interaction between the beam and the wave and becomes waste space inside of the tube. Waste space is eliminated, a tube having a smaller diameter can be made. Also, in this tube a negative electrode, termed the sole, is mounted inside of the tube cylinder. Supporting structures for the sole tend to add to the thickness of the gap between the magnet and the interaction space, thereby necessitating the use of a larger magnet than would otherwise be employed. Likewise,

the radial projections for the exhaust tubulation and the external leads decrease the possibility of using a magnet which otherwise could be mounted along the circumference of the tube.

This invention involves a novel sole and cathode mount ing assembly wherein all leads for the sole, cathode and anode are brought into the tube through a rigid coaxial lead-in assembly. The lead-in assembly is mounted along the axis of a cylindrical tube and is perpendicular to a cover thereof. Likewise, the exhaust tubulation is mounted on a back cover of the tube. Thus, all radial projections, except for a coaxial output line, on the circumferential wall of the tube are eliminated. The lead-in assembly also provides an excellent support for the sole cathode assembly and consumes a minimum of the space between the faces of the tube. Therefore, a tube of smaller diameter may be made because the sector of space otherwise needed for the leads and the exhaust tubulation may be usefully employed. Also, a smaller magnet gap is obtained since the sole and cathode are held in position by the lead-in assembly rather than by a mounting plate within the tube. Furthermore, insulating bushings which are subject to breakage and loosening due to thermal cycles, may be eliminated.

if this This invention and the features thereof will be under stood more clearly and fully from the following detailed description of one embodiment of the invention with reference to the accompanying drawings wherein:

FIG. 1 is a front view of the cathode assembly;

FIG. 2 is a top view of FIG. 1;

FIG. 3 is a cross-sectional view of FIG. 1 taken along line 3-3;

FIG. 4 is a sectional view of a microwave oscillator made in accordance with this invention; and

FIG. 5 is a cross-sectional view of FIG. 4 having a broken away section showing the interdigital delay line and the collector.

Referring now to FIGS. 1, 2 and 3, a cathode assembly of the type used in the oscillator tube is shown. This assembly consists of a cathode 1, which in this embodiment may be a thin ribbon of tungsten, for example, supported by a pair of metal connectors 2 and 3. The action of an insulated spring support 4, which maintains a lateral pressure on the connectors 2 and 3 is used to keep the cathode 1 in a rigid position. The spring support 4 is properly held in place with a clamp 5 which is in turn connected to a spacer 6 and an inner wall 7 of the sole section 8 with a pair of screws and it The connectors 2 and 3 are joined to a pair of supports 11 and 12 which are bolted to a pair of brackets 13 and 14 with a set of screws 15 and nuts 16. The connectors 2 and 3 are insulated from the brackets 13 and 14 with a set of insulators 17. The brackets 13 and 14 are also connected to the wall 7 of the sole section 8 by a set of screws not shown. The sole section 8 becomes a part of the circumferential wall of the sole when the cathode assembly is fitted into the entire oscillator tube assembly. A group of six end shields 18, i9, 26, 21, 22 and 23 are affixed to the top and bottom of the sole section 3 with a set of eight screws 24, which are threaded through the shields as shown. The end shields 1? and 22 are each provided with openings 25 and 26, respectively, through which the cathode 1 extends. Thus, it may be seen that if suitable connections are made from a power supply to the cathode assembly, the tungsten cathode strip 1 will act as the source of an electron beam.

Referring now to FIGS. 4 and 5, which illustrate a microwave oscillator made in accordance with this invention, a cathode assembly 27, of the type described above, is shown mounted within the oscillator tube and connected to a sole 39. The sole, which is primarily a cylindrical shell of electrically-conductive material, has a recessed center surface containing a plurality of holes extending thcrethrough. It may be seen that the center hole 42 in the sole 39 is designed to facilitate the ease with which a lead-in assembly 28 may be connected thereto. The lead-in assembly 28 is perpendicular to a top cover 29 of the tube, and the axis of the lead-in assembly coincides with that of the sole. Thus, the lead-in assembly not only supports the sole 39 and the cathode assembly 27 in a position adjacent to and concentric with an anode assembly 34 but also contains the electrical lead lines whereby the tube may be made to operate.

Referring to FIG. 4, the elongated lead-in assembly 28 consists of a series of telescopically disposed cylindrical lead lines or conductors which are insulated one from the other and are connected to the cathode, anode and sole. In this embodiment of the invention, the cathode 1 is directly heated by passing a current through it. Thus, a current may be passed through a cap 31 which is attached internally to a cylindrical central conductor 32 and thence into a connecting member 33. The connecting member 33 is welded onto the end point of the conductor 32 and connected at its other end to a screw 15 in the cathode assembly 27. The current may then pass through a connector 3 into the cathode 1, thereby sutficiently heating the cathode to cause electron emission. The circuit is completed, as shown in FIG. 5, through a second connector 2, a support 11, a nut 16, and a second connecting member 34, which extends through a hole 35 in the sole to join a third connecting member 36. The connecting member 36 is shown in FIG. 4 attached to an intermediate cylindrical conductor 37 which is in turn connected to an external terminal 38.

Likewise, the sole 39 may be negatively biased by applying the desired potential to an outer cylindrical conductor 40 through an external terminal 41 on the lead-in assembly 28. It should be noted that the sole section 8, shown in FIG. 3, is a part of the cylindrical shell which comprises the entire circumferential wall of the sole 39. The outer conductor 41) also acts as the main support for the sole 39 and cathode assembly 27 and may be welded to the sole along the rim of a center hole 42 provided in the sole. An external terminal 43 may be welded to the top cover 29 which is in turn connected to the anode assembly 30. Thus, the anode assembly may be biased at the desired positive potential. It should be noted that the external terminals 31, 38, 41 and 43 are supported and insulated from each other by three cylindrical glass sections 44, 45 and 46.

The anode assembly 30, shown in FIGS. 4 and S is a cylindrically-shaped wave guide delay line comprised of a plurality of interdigital fingers 47 attached in alternate sequence to end flanges flanking the centrally disposed internal ridge integral with the supporting rim of the assembly. Fingers 47 are separated from the circumferential surface or wall 48 of the sole 39 to form an interaction space 49 wherein an electron beam generated by the cathode 1 may pass. The delay line 47 is terminated at one end by an attenuator comprising an absorbing material which is placed over the fingers, and at the other end the delay line is terminated at a finger which is connected to a coaxial output line 50. The output line 50 is sealed in an opening provided in the tube as shown and is impedance matched to the delay line 47. The anode assembly 30 is also provided with an electron interceptor or collector 51, the function of which is to prevent electrons from re-entering the area adjacent to the cathode 1. The section of the collector 51 which projects into the interaction space 49 should be made of sufiicient size so that for all anode voltages at which the tube is designed to operate, the electrons entering this area of the tube will be intercepted. It should also be noted that the end shields, such as end shields 18, 19 and 20, shown in FIG. 5, prevent the electrons from escaping from the interaction space 49 in a lateral direction. The tube is closed with a back cover 52, as shown in FIG. 4, through which an exhaust tubulation 53 extends. This tubulation is rovided as a means whereby the tube can be evacuated and it may be pinched off to hermetically seal the sole 39, cathode assembly 27 and the anode assembly Stl. Thus, the front cover 29, the back cover 52 and the outer wall of the anode assembly 30 provide the internal components of the tube with an air-tight envelope. A cap 54 is provided to protect the pinched off section of the tubulation 53. The oscillator tube may be cooled by passing water through a small pipe, not shown, which may be brazed to the outer wall of the anode assembly 30. The magnetic field, which should be transverse to the direction of flow of the electron beam, may be provided by a permanent magnet, not shown, radially positioned on the tube. The magnetic lines of force for the particular tube described herein should continuously flow from left to right in relation to the interaction space 49, shown in FIG. 4, and should flow out of the paper in regard to the view shown in FIG. 5.

The operation of the tube may be described with reference to FIG. 5. The electron beam, generated by heating the cathode 1, until it is electron emissive, flows around the interaction space 49 in a counter-clockwise direction due to the influence of the transversely dispose magnetic field described above. By biasing the anode 30 and the interdigital fingers 47 with a positive potential and the sole 39 with a negative potential, the electron flow may be controlled as described. Therefore, as the radio frequency energy generated in the interaction space 49 begins to travel along the periodic structure of the anode 3t), the electromagnetic fields associated therewith will contain some waves which will travel in a direction opposite to that of the flow of energy. Thus, the electron beam, which is maintained at a velocity synchronous with the phase velocity of the wave, will interact with the backward traveling wave and will give energyto the wave. This energy travels toward the source of the beam thereby modulating the beam in its earlier stages. When the beam current becomes sufficiently large, this action becomes self-sustaining and the tube will oscillate. The energy given to the wave, therefore, travels in a clockwise direction toward the coaxial output line 50 and may be extracted at that end of the delay line 47 and fed to a. load. Since the electron velocity determines the frequency of oscillation and is proportional to the anode voltage, the frequency may be controlled by varying the anode voltage. If there is a good match between the line and the load, most of the energy produced will reach the load. If there is a mismatch, the energy will be reflected and will travel toward the collector end of the tube where it is absorbed by the attenuated interdigital fingers. Electrons not intercepted by the anode structure will be intercepted by the collector 5 1 and dissipated as heat.

As previously mentioned, the novel sole-cathode support assembly provides the tube with a smaller magnet gap because a sole-mounting plate is no longer necessary as a separate support for the sole. Also, a tube of smaller diameter may be made because waste space within the tube is decreased by repositioning the lead-in assembly and the exhaust tubulation, as described, and packaging with a permanent magnet positioned along the circumference of the tube is facilitated.

However, it should be understood that this invention is not limited to the particular details described above, as many equivalents will suggest themselves to those skilled in the art. For example, the conductors in the lead-in assembly need not be coaxial or telescopically disposed, and the relative positions of the lead-in asesmbly and exhaust tubulation could be reversed. Likewise, the cathode could be separately rather than directly heated. Therefore, it is desired that the appended claims be given a broad interpretataion commensurate with the scope of the invention within the art.

What is claimed is:

1. An electron discharge device comprising a cylindrical anode structure having a centrally apertured closure plate, an outer tube supported upon said closure plate, an inner tube having a substantial area of its outer surface in contact with said outer tube for support by said outer tube, said tubes being arranged along the longitudinal axis of said structure, an auxiliary electrode concentric with said structure and supported from said inner tube, and a cathode element carried by said auxiliary electrode at a position within said anode structure.

2. An electron discharge device comprising a cylindrical anode structure having a centrally apertured closure plate, an outer tube supported upon said closure plate along the centrally apertured portion thereof, an inner tube supported by said outer tube and in electrically insulating relation with said outer tube said tubes being disposed along the axis of said cylindrical anode structure, a cathode element, an auxiliary electrode concentric with said anode structure, and means for supporting said cathode element from said auxiliary electrode adjacent the outer edge of said auxiliary electrode.

3. An electron discharge device comprising a cylindrical slow wave propagating structure, a casing enclosing said structure, said casing having a centrally apertured closure plate, an outer tube supported up n sai closure plate, an inner tube supported upon said outer tube, an auxiliary electrode concentric with said structure and supported from said inner tube, and a cathodecarrying assembly supported upon said auxiliary electrode.

4. An electron discharge device as defined in claim 3, and including a cathode element carried upon said cathode-carrying assembly in a position adjacent the periphery of said assembly, and in proximity to said output delaying structure.

5. An electron discharge device comprising an anode structure having concentric inner and outer cylindrical peripheries of relatively wide diameter, an auxiliary electrode concentric with said anode structure and almost completely filling the broad chamber bounded by said inner cylindrical periphery, a cathode assembly including a cathode element in the form of a thin metallic strip having its longer edges parallel to but widely spaced from the longitudinal axis of said concentric peripheries, said cathode asesmbly being supported from said auxiliary electrode, and means including concentric conductors extending along said longitudinal axis for completing the electrical circuit of said cathode.

6; An electron discharge device comprising an anode structure having concentric inner and outer cylindrical peripheries of relatively wide diameter, an auxiliary electrode concentric with said anode structure and almost completely filling the broad chamber bounded by said inner cylindrical periphery, and a cathode assembly including a thin metallic strip having its longer edges parallel to the longitudinal axis of said concentric peripheries, said cathode assembly being supported from said auxiliary electrode adjacent the outer edge of said auxiliary electrode.

7. An electron discharge device comprising a cylindrical slow wave propagating structure having a centrally apertured closure plate of relatively wide diameter, an outer tube supported from said closure plate, an inner tube located within said outer tube and extending within said cylindrical structure, said inner tube supported by and electrically insulated from said outer tube by an electrical insulator, and a sole element located within said cylindrical structure and attached to said inner tube.

8. An electron discharge device comprising a cylindrical slow wave propagating structure having a centrally apertured closure plate of relatively wide diameter, an outer tube supported from said closure plate, an inner tube located within said outer tube and extending within said cylindrical structure, said inner tube supported by and electrically insulated from said outer tube by a first electrical insulator, a sole element located within said cylindrical structure and attached to said inner tube, and a cathode assembly supported by and insulated from said sole element by a second electrical insulator.

9. An electron discharge device comprising a cylindrical slow Wave propagating structure having a centrally apertured closure plate of relatively wide diameter, an outer tube supported from said closure plate, an inner tube located within said outer tube and extending within said cylindrical structure, said inner tube supported by and electrically insulated from said outer tube by a first electrically insulating means, a sole element located Within said cylindrical structure and attached to said inner tube, and a cathode assembly supported by and insulated from said sole element by a second electrically insulating means.

10. An electron discharge device comprising a cylindrical slow wave propagating structure having a centrally apertured closure plate of relatively wide diameter, an outer tube supported from said closure plate, an inner tube located Within said outer tube and extending within said cylindrical structure, said inner tube supported by and electrically insulated from said outer tube by a first electrically insulating means, a sole element located within said cylindrical structure and attached to said inner tube, a cathode assembly supported by and insulated from said sole element by a second electrically insulating means, and electrical connecting means located within said inner tube and passing through said second electrically insulating means thereby providing electrical connections with said cathode assembly.

11. An electron discharge device comprising an anode structure having concentric inner and outer cylindrical peripheries of relatively wide diameter, an auxiliary electrode concentric with said anode structure and almost completely filling the broad chamber bounded by said inner cylindrical periphery, a cathode assembly including a cathode, said cathode assembly being supported from said auxiliary electrode and electrically insulated therefrom, and tubular means containing electrically-conductive leads connected respectively to said auxiliary electrode said cathode and said anode structure for maintaining said auxiliary electrode said cathode and said anode structure at appropriate operating potentials, said tubular means further providing support for said auxiliary electrode.

References Cited in the file of this patent UNITED STATES PATENTS 2,497,436 Brown Feb. 14, 1950 2,509,419 Brown May 30, 1950 2,531,972 Doehler et al Nov. 28, 1950 2,542,899 Brown Feb. 20, 1951 2,607,904 Ler-bs Aug. 19, 1952 2,611,110 Powers Sept. 16, 1952 2,681,427 Brown et a1 June 15, 1954 2,760,111 Kumpfer Aug. 21, 1956 2,832,005 Brown Apr. 22, 1958 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,027,483 March 27, 1962 Edward C. Dench It is hereby certified that error a ent requiring correction and that the sa corrected below.

ppears in the above numbered pat id Letters Patent should read as Column 4, line 4, for "described" read desired line 66, after "tube" insert a comma; column 5, line 54, for

"sceond" read second Signed and sealed this 2nd day of October 1962.

SEAL) .ttest:

{NEST w. SWIDER DAVID LADD ttesting Officer Commissioner of Patents 

